LSMW in ECC6.0

Dear SAP Gurus,
I want to create an LSMW for uploading GL Accounts Master Data in ECC6.0. I have reached till the step of Read Data and now stuck.
On executing Read Data the system issues me a message:
"Loading from front end is not all packed/hexadec. fields"
Although it is a WARNING message the system does not allow me to go further.
The only button available to me is 'Enter' and when I hit enter NOTHING HAPPENS.
PLEASE HELP !
Many Thanks
Rajesh